The radiograph and MRI demonstrate osteonecrosis of the knee. Spontaneous osteonecrosis occurs most commonly in females over 55 years of age and most frequently involves the medial femoral condyle. Treatment is arthroplasty when conservative management fails. Open biopsy is incorrect as there is no matrix or periosteal reaction suspicious for malignancy and primary malignancy in a 59-year-old would be rare. Chest CT and bone scan is incorrect as the subchondral femoral condyle is not a site of bony metastases and the patient is otherwise healthy. Osteochondral autograft would be a poor choice given the size of the defect and the patient's age. HTO would be a poor choice for a 59-year-old and there is no significant varus deformity present. In a systematic review, Myers found that TKA and UKA treatment for spontaneous ostenecrosis achieved similar results compared to TKA/UKA for osteoarthritis when the appropriate indications are exercised.
Barrack. Orthopaedic Knowledge Update: Hip and Knee Reconstruction. 3rd edition. AAOS: January 10, 2006.
Myers TG, Cui Q, Kuskowski M, Mihalko WM, Saleh KJ. Outcomes of total and unicompartmental knee arthroplasty for secondary and spontaneous osteonecrosis ofthe knee. J Bone Joint Surg Am. 2006 Nov;88 Suppl 3:76-82.
PMID:17079371 (Link to Abstract)